I have the best of reasons for being an admirer of Werner Heisenberg. He and I were young research students at the same time, about the same age, working on the same problem. Heisenberg succeeded where I failed. There was a large mass of spectroscopic data accumulated at that time and Heisenberg found out the proper way of handling it. In doing so, he started the golden age of theoretical physics...

One can distinguish between two main procedures for a theoretical physicist. One of them is to work from the experimental basis. For this, one must keep in close touch with the experimental physicists. One reads about all the results they obtain and tries to fit them into a comprehensive and satisfying scheme.

The other procedure is to work from the mathematical basis. One examines and criticizes the existing theory. One tries to pin-point the faults in it and then tries to remove them. The difficulty here is to remove the faults without destroying the very great success of the existing theory...

This is illustrated by the discovery of quantum mechanics. Two men are involved, Heisenberg and Shrodinger. Heisenberg was working from the xperimental basis, using the results of spectroscopy, which by 1925 had ccumulated an enormous amount of data... It was Heisenberg's genius hat he was able to pick out the important things from the great wealth f information and arrange them in a natural scheme. He was thus led to mtrices...

Schrodinger's approach was quite different. He worked from the mathematical basis. He was not well informed about the latest spectroscopic results, lke Heisenberg was, but had the idea at the back of his mind that spectral requencies should be fixed by eigenvalue equations, something like those hat fix the frequencies of systems of vibrating strings. He had this idea for a long time, and was eventually able to find the right equation, in an indirect way...

Heisenberg and Schrodinger gave us two forms of quantum mechanics, which were soon found to be equivalent. They provided two pictures, with a certain mathematical transformation connecting them. I joined in the early work on quantum mechanics, following the procedure based on mathematics, with a very abstract point of view. I took the noncommutative algebra which was suggested by Heisenberg's matrices as the main feature for a new dynamics...